The present invention relates to a device in an oil/gas treatment plant where excess gas from a number of sources is intercepted and is led through a collection conduit for advancing for recovery.
By oil/gas treatment plant is meant plant for oil production where hydrocarbon gases are separated from the Oil, refining plant, plus all types of processing plants from which combustible gases are formed which must be handled in a separate plant.
1. Field of the Invention
The invention has particular application in connection with oil production plants where the gaseous hydrocarbons are separated from the oil. Such plants comprise separate collection conduits for the leading away of excess gases to a flame tower where the gases are either released directly out into the atmosphere (cold torch) or burned off. The collection conduit systems are connected via conduits having valves to their respective separators and compressors in the plant. When an abnormal situation, such as too high a gas pressure, leakages, conduit breakage and the like, arises in one of these conduit systems or apparatuses, associated measuring instruments will register this and open associated valves so that the excess gases are led into the collection conduit system. However it often happens that such valves are not closed satisfactorily after they have been in operation, and therefore they continue to leak gases into the collection conduit system. Repairs of such valve leakages however must as a rule be postponed until the usual periodic examination of the plant.
When the excess gas is burned off the collection conduit must as a rule be supplied with a combustible gas in order to obtain a uniform gas supply for maintaining a flame in the flame tower, while when the gas is to be released unburned out into the atmosphere an inert gas is often supplied. In a normal operating situation the combustible gas feeds constitute, together with the said valve leakage gases (that is to say processing gases) the main sources for that excess gas which is burned off in the flame tower. There is consequently a continuous need for diverting and possibly burning off excess gases in a flame. Measurements have shown that the volume of gas which is released or burned off per twenty four hours can constitute up to 36000 m.sup.3 per plant.
In society there is increasing interest in the condition of the environment, and one is particularly aware of the escape of air gases, such as CO.sub.2, which can produce the so-called greenhouse effect. In this connection it is desirable to reduce the extent of the escape of torch gases. Furthermore it is clear that the excess gases represent a significant resource and that a better utilisation of the excess gases, in addition to the environmental, will also yield a contribution positive to the economy of the plant.
2. Description of Related Art
There are processes described hitherto for the recovery of excess gases in the treatment of oil products, which include a plant where excess gases are burned off in a flame tower.
In GB-Patent Application 2.066.936 a refining plant for oil is disclosed where excess gases in the form of hydrocarbon fractions are to be recovered. These excess gases are diverted from a torch conduit system and are condensed in one or more steps by compression and cooling down whereby the condensate is led back to the process. The gas residue however is led out into a torch tower and burned off. Thus according to the known solution the intention is that the residue amounts of hydrocarbon gases shall still be led continuously to the flame tower, or alternatively these residue gases shall be used as a fuel gas.
In DD-Patent Specification 266.006 a plant is disclosed for conducting together from several sources combustible gases having very dissimilar compositions into two main streams. The joint conduction is controlled by means of computers which regulate the mixture based on measurements of the calorific value of the gases. In this case there is also included a torch system.